Inflatable folding wings for a very high altitude aircraft

ABSTRACT

A foldable wing for use with a very high altitude aircraft capable of operating at an altitude at or above 85,000 feet is disclosed. The foldable wing may employ a spiral fold deployment, wherein a hinge between each segment of the foldable wing is slightly offset from the perpendicular. Successively positioned wing segments fold over one another. Alternatively, the hinges are substantially perpendicular so that each respective wing segment folds linearly against the next wing segment. An inflatable rib, with inflatable arms, can be inflated to provide a force against two adjacent arms, thereby deploying the wing segments through a full 180° of rotation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/358,036, filed Jan. 22, 2009, which claims priority to U.S. PatentApplication No. 61/023,075, filed Jan. 23, 2008, the entire contents ofwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a wing structure for aircraft. Moreparticularly, the invention relates to an apparatus, and method for itsuse, of a folding wing structure for a very high altitude aircraft. Thisparticular invention combines both inflatable and rigid hinged elements.

2. Background Art

For aircraft that operate at very high altitudes, the wing structure isa very important criterion. Very high altitudes means altitudes betweenabout 85,000 feet and about 150,000 feet above sea level (ASL). At thesealtitudes, air densities are very low, and therefore generally, wingstructures need to be relatively large areas compared to a similarlysized aircraft operating at lower altitudes of, for example, about35,000 to 45,000 feet ASL, in order to generate the lift necessary tofunctionally fly.

Furthermore, if an aircraft is developed to operate at such altitudes,it is desirable to allot as much weight as possible to payload (e.g.,sensors, and things of that nature), and to minimize unnecessary weightexpenditures wherever possible. As a result, the use of compositematerials has recently increased. If the wings could be made ofcomposite and/or inflatable materials, yet still provide the wing areaand lift necessary to properly operate at the desired high altitudes, anenormous operating benefit can be obtained.

Because of recent historical developments, a need has been developed toplace unmanned aerial vehicles to locations literally around the groundwithin several hours notice. One manner of deployment can be viarockets, launched from ground locations and/or ocean-going ships. Inthese cases, the aircraft would have to be foldable and be able toquickly begin operating at high altitudes upon deployment from therocket.

Thus, a need exists to develop a foldable aircraft, with foldableinflatable wings that can operate at very high altitudes.

SUMMARY OF THE INVENTION

It is therefore a general aspect of the invention to provide a very highaltitude foldable inflatable aircraft that will obviate or minimizeproblems of the type previously described.

According to a first aspect of the present invention, a foldableaircraft is provided comprising an inflatable rib for use in a wing of avery high altitude aircraft capable of operating at an altitude at orabove 85,000 feet, the inflatable rib comprising: a plurality of tubesincluding an innermost tube; a plurality of outer connecting surfaces,wherein the outer connecting surface connects one of the plurality oftunes to an adjacent one of the plurality of tubes; an innermostconnecting surface that connects an inner perimeter of the innermosttune to itself; and a linking tube that is connected to each of theplurality of tubes, and is configured to receive gas and to distributethe received gas to the plurality of tubes, thereby inflating each ofthe tubes to form the inflatable rib.

The gas may comprise a high pressure gas having a pressure at or above10 pounds per square inch (psi). The gas may be generated by a pressuretank, a chemical reaction gas generator, or a propulsion systemassociated with the very high altitude aircraft. Each of the pluralitytubes may be substantially cylindrical.

According to a second aspect, an inflatable rib for use in a wing of avery high altitude aircraft capable of operating at an altitude at orabove 85,000 feet, is provided, the inflatable rib comprising: a singleinflatable structure substantially configured to function as a wing rib,and configured to receive a high pressure gas generated by an externalgas generating source, wherein the high pressure gas has a pressure ator above 10 psi. The external gas generating source may comprise apressure tank, a chemical reaction gas generator, or a propulsion systemassociated with the very high altitude aircraft.

According to a third aspect, a wing segment is provided comprising atleast two inflatable ribs, wherein a wing flexible skin between the ribsis supported by and maintained in a predetermined airfoil shape by aseries of stringers and a trailing edge. At least one of the stringersand/or the trailing edge may comprise an inflatable tube. Alternatively,at least one of the stringers and/or the trailing edge may comprise arigid shape made from a metal and/or one or more composite materials.Each of the stringers may comprise one or more rigid materials on anexterior of the wing segment and an inflatable tube inside the wingsegment, wherein the inflatable tube is configured to provide stiffnesswith a predetermined stowed volume and to provide a predetermined wingsegment shape.

According to a fourth aspect, a foldable wing structure for use in avery high altitude aircraft capable of operating at an altitude at orabove 85,000 feet is provided, the foldable wing structure comprising: asemi-rigid spar, configured to receive and distribute a first gas; atleast two or more inflatable ribs, each inflatable rib being connectedto the semi-rigid spar; a plurality of inflatable stringers, whereineach of the plurality of inflatable stringers is connected to at leasttwo ribs, and wherein each of the plurality of inflatable stringers isconfigured to receive and distribute a second gas to the at least two ormore inflatable ribs; a plurality of rigid trailing edge tubes, whereineach of the plurality of rigid trailing edge tubes is attached to atleast two inflatable ribs; and an inflatable leading edge apparatusconfigured to receive the first gas from the semi-rigid spar. When theat least two or more inflatable foldable ribs, the plurality ofinflatable stringers, and the inflatable leading edge apparatus are inan un-inflated condition, the foldable wing structure is configured tobe folded such that a chord of the foldable wing structure has a lengthof between approximately 25 percent and 50 percent of a length of amaximum respective chord, and when the at least two or more inflatablefoldable ribs, the plurality of inflatable stringers, and the inflatableleading edge apparatus are in an inflated condition, the foldable wingstructure is configured to be unfolded such that the length of the chordof the foldable wing structure is approximately equal to the length ofthe maximum respective chord.

The first gas may comprise a low pressure gas having a pressure at orbelow 0.1 psi. The second gas may comprise a high pressure gas having apressure at or above 10 psi. The first gas and the second gas may begenerated by a pressure tank, a chemical reaction gas generator, or apropulsion system associated with the very high altitude aircraft. Thelow pressure gas may comprise atmospheric ram pressure from an air scoopon the aircraft.

According to a fifth aspect, a leading edge segment for use in afoldable wing in a very high altitude aircraft capable of operating atan altitude at or above 85,000 feet is provided, wherein the foldablewing includes a spar that receives and distributes a first gas. Theleading edge segment comprises: a semi-rigid shell shaped in a form of aleading edge of the foldable wing, the semi rigid shell being hingedlyconnected to the spar; a flexible membrane connected to a lowermostportion of the semi-rigid shell and to the spar, thereby forming achamber within the semi-rigid shell and being configured to accept andretain the first gas; and a passageway between the spar and thesemi-rigid shell, wherein the passageway is configured to enable atransfer the first gas from the spar to the chamber.

The first gas may comprise a low pressure gas having a pressure at orbelow 0.1 psi. The first gas may be generated by a pressure tank, achemical reaction gas generator, or a propulsion system associated withthe very high altitude aircraft.

The leading edge may be configured to be deployed as a result of a highpressure gas inflating at least one bladder between the leading edge andthe spar, wherein the high pressure gas has a pressure at or above 10psi.

According to a sixth aspect of the present invention, a foldable wingfor use in a very high altitude aircraft capable of operating at analtitude at or above 85,000 feet is provided. The foldable wingcomprises: a first spar section, a second spar section, and a third sparsection, wherein the first spar section is positioned closest to afuselage of the very high altitude aircraft, the second spar section ispositioned adjacent to the first spar section, and the third sparsection is positioned adjacent to the second spar section, and farthestaway from the fuselage; a first hinge and a second hinge, wherein thefirst hinge rotationally connects the first spar section to the secondspar section at a first angle, and wherein the second hinge rotationallyconnects the second spar section to the third spar section at the firstangle, and further wherein the third spar section is configured torotate about 180° such that an outermost portion of the third sparsection is located above an innermost portion of the second sparsection, and further wherein the second spar section is configured torotate about 180° such that an outermost portion of the second sparsection is located above an innermost portion of the first spar section,and the outermost portion of the third spar section is located above anoutermost portion of the first spar section.

The foldable wing according to the sixth aspect may further comprise atleast a fourth spar section and a third hinge, the fourth spar sectionbeing configured to rotate about 180° such that an outermost portion ofthe fourth spar section is located above an innermost portion of thethird spar section. The first angle may have a measure of between about1° and about 4°.

According to a seventh aspect of the present invention, a foldable wingfor use in a very high altitude aircraft capable of operating at analtitude at or above 85,000 feet is provided, the foldable wingcomprising: a first, second and third spar section, wherein the firstspar section is closest to a fuselage of the very high altitudeaircraft, the second spar section is adjacent to the first spar section,and the third spar section is adjacent to the second spar section, andfarthest away from the fuselage; a first hinge and a second hinge,wherein the second hinge is connected to the second spar section andthird spar section at a first angle, and wherein the second hinge isconfigured to rotate the third spar section about the second sparsection at the first angle such that a farthest-most portion of thethird spar section is located above an innermost portion of the secondspar section, and further wherein the first hinge is connected to thefirst spar section and the second spar section at the first angle, andwherein the first hinge is configured to rotate the second spar sectionabout the first spar section at the first angle such that afarthest-most portion of the second spar section is located above aninnermost portion of the first spar.

According to the seventh aspect, the first angle is between about 1° andabout 4°, and wherein additional spar sections and hinges can be addedsuch that each can rotate and fold over an inner adjacent spar section.

According to an eighth aspect of the present invention, a foldable wingfor use in a very high altitude aircraft capable of operating at analtitude at or above 85,000 feet is provided. The foldable wingcomprises: a plurality of hinges; a plurality of spar sections, whereineach of the plurality of spar sections is configured to receive andtransfer a first gas, and wherein each of the plurality of hingesrotationally connects a respective spar section to an adjacent sparsection; and a plurality of inflatable ribs, wherein each of theinflatable ribs includes a rib section, a first arm, and a second arm,and wherein the first arm is positioned adjacent to a respective sparsection, and the second arm is positioned adjacent to an adjacent sparsection, and wherein the first arm is configured to inflate when thefirst arm receives the first gas, and the second arm is configured toinflate when the second arm receives the first gas. Upon inflation, thefirst arm and second arm are further configured to cause the respectivespar section and the adjacent spar section to rotate with respect to oneanother until the respective spar section and the adjacent spar sectioncouple with one another. The rib is configured to inflate until the ribhas a substantially perpendicular orientation with respect to thecoupled spar sections.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features and advantages of the present invention will best beunderstood by reference to the detailed description of the preferredembodiments that follows, when read in conjunction with the accompanyingdrawings, in which:

FIGS. 1A-1F illustrate a very high altitude aircraft with foldable wingsaccording to an embodiment of the present invention.

FIGS. 2A-2C illustrate a foldable wing structure as it unfolds accordingto an embodiment of the present invention.

FIG. 3 illustrates a folding wing structure according to an embodimentof the present invention.

FIG. 4 illustrates a side view of an inflatable rib for use in afoldable wing in a very high altitude aircraft according to anembodiment of the present invention.

FIGS. 5A and 5B illustrate cross-sectional views of the inflatable ribshown in FIG. 4.

FIG. 6 illustrates a perspective view of a foldable wing and aninflatable rib according to an alternate embodiment of the presentinvention.

FIG. 7 illustrates a cross-sectional side view of a foldable wing anddrooping leading edge structure according to according to an embodimentof the present invention.

FIG. 8 illustrates another cross-sectional view of the inflatable wingshown in FIG. 7 following inflation of the drooping leading edgestructure according to an embodiment of the present invention.

FIGS. 9-13 illustrate a sequence of perspective views of a foldable wingstructure, as the foldable wing structure folds to a storage position,and wherein foldable wing segments are connected by hinges that arecanted at a first angle according to an embodiment of the presentinvention.

FIGS. 14A-14D illustrate several views of a foldable wing structurewherein foldable wing segments are connected by hinges that are notcanted at a first angle.

FIGS. 15A-15G illustrate several views of the foldable wing structureshown in FIGS. 9-13 according to an embodiment of the present invention.

FIGS. 16 and 17 illustrate a foldable rib and spar extending structureaccording to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The various features of the preferred embodiments will now be describedwith reference to the drawing figures, in which like parts areidentified with the same reference characters. The following descriptionof the presently contemplated best mode of practicing the invention isnot to be taken in a limiting sense, but is provided merely for thepurpose of describing the general principles of the invention.

I. Deployment of Very High Altitude Aircraft

FIGS. 1A-1F illustrate deployment of a very high altitude aircraft (VHAaircraft) 100 according to an embodiment of the present invention. VHAaircraft 100, as shown in FIGS. 1A-1F, can be deployed by various means,including other high altitude operating aircraft (i.e., hypersonicaircraft), rockets and other means. As shown in FIGS. 1A-1F, VHAaircraft 100 is deployed at a very high altitude in a rocket. Accordingto an exemplary embodiment of the present invention, VHA aircraft 100 isstored within fairing 2 of the rocket, at the nose section. Because VHAaircraft 100 is deployed via a rocket, VHA aircraft 100 can be deployedanywhere on the globe within an hour or two from a decision to launch.Such a rapid deployment provides the ability to rapidly acquirepertinent and timely information, in many cases hours, days or weeksbefore other more conventional information gathering resources,including satellites, can be similarly deployed. According to anembodiment of the present invention, very high altitude comprisesaltitudes between about 85,000 feet above sea level, and about 150,000feet above sea level.

FIG. 1E illustrates left wing foldable structure 8 a after all threeleft wing foldable segments 12 a-c have unfolded and locked together.The unfolding of each left wing foldable structure 12 a-c and lockingtogether of spars 16 will be described in greater detail below. As thoseof ordinary skill in the art of the present invention can appreciate,there can be one, two, three or more wing foldable segments 12 for VHAaircraft 100. According to a preferred embodiment of the presentinvention, the number of left wing foldable segments 12, and right wingfoldable segments 14 will be equal, though that need not always be thecase. Finally, as shown in FIG. 1F, foldable left wing structure 8 a isfully extended and fully inflated. FIGS. 2A-2C illustrate an unfoldingof foldable left wing structure 8 a from a different perspective thanthat shown in FIGS. 1A-1F according to an embodiment of the presentinvention. In FIGS. 2A-2C, foldable left wing structure 8 a, and inparticular first left wing foldable segment 12 a, is shown as it unfoldsto an extended state (FIG. 2C). In FIG. 2A, left wing foldable segment12 a is un-extended (i.e., not inflated); in FIG. 2B, left wing foldablesegment 12 a is extended, but not yet completely inflated. Ribs 26 havebeen inflated, extending wing covering 18 to the full width of foldableleft wing structure 8 a, as shown by the direction of arrows B. Foldableleft wing structure 8 a now takes a more wing-like shape or form, thoughit is not yet capable of generating lift, because wing covering 18 hasnot been pulled taut. Leading edge segment 20 folds up, as arrow Aindicates. In FIG. 2C, ribs 26 are completely inflated, creating adefinite shape to foldable left wing structure 8 a; stringers 30 areinflated, and cause foldable left wing structure 8 a to expand in thedirection of arrows C and D; and trailing edge segments 24 can also beinflated at this time.

FIG. 1E illustrates left wing foldable structure 8 a after all threeleft wing foldable segments 12 a-c have unfolded and locked together.The unfolding of each left wing foldable structure 12 a-c and lockingtogether of spars 16 will be described in greater detail below. As thoseof ordinary skill in the art of the present invention can appreciate,there can be one, two, three or more wing foldable segments 12 for VHAaircraft 100. According to a preferred embodiment of the presentinvention, the number of left wing foldable segments 12, and right wingfoldable segments 14 will be equal, though that need not always be thecase. Finally, as shown in FIG. 1F, foldable left wing structure 8 a isfully extended and fully inflated. FIGS. 2A-2C illustrate an unfoldingof foldable left wing structure 8 a from a different perspective thanthat shown in FIGS. 1A-1F according to an embodiment of the presentinvention. In FIGS. 2A-2C, foldable left wing structure 8 a, and inparticular first left wing foldable segment 12 a, is shown as it unfoldsto an extended state (FIG. 2C). In FIG. 2A, left wing foldable segment12 a is un-extended (i.e., not inflated); in FIG. 2B, left wing foldablesegment 12 a is extended, but not yet completely inflated. Ribs 26 havebeen inflated, extending wing covering 18 to the full width of foldableleft wing structure 8 a, as shown by the direction of arrows B. Foldableleft wing structure 8 a now takes a more wing-like shape or form, thoughit is not yet capable of generating lift, because wing covering 18 hasnot been pulled taut. Leading edge segment 20 folds up, as arrow Aindicates. In FIG. 2C, ribs 26 are completely inflated, creating adefinite shape to foldable left wing structure 8 a; stringers 22 areinflated, and cause foldable left wing structure 8 a to expand in thedirection of arrows C and D; and trailing edge segments 24 can also beinflated at this time.

According to a preferred embodiment of the present invention, when ribs26, stringers 30, and leading edge segment 20 are in an un-inflatedcondition, foldable wing structure 12 is configured to be folded suchthat a width of foldable wing structure 12 is between approximately 25percent and 50 percent of a maximum chord width.

According to a preferred embodiment of the present invention, when ribs26, stringers 30, and leading edge segment 20 are in an inflatedcondition, foldable wing structure 12 is configured to be unfolded suchthat the width of foldable wing structure 12 is approximately equal tothe maximum chord width.

According to a preferred embodiment of the present invention, when ribs26, stringers 26, and leading edge segment are in an inflated condition,foldable wing structure 12 is configured to be unfolded such that thewidth of foldable wing structure 12 is approximately equal to themaximum chord width.

FIG. 3 illustrates a front perspective view of left wing foldablesegment 12 showing flow of high pressure gas and low pressure gas withinat least one inflatable wing structure. According to a preferredembodiment of the present invention, low pressure gases range in valueof psi at or below 1 psi, and high pressure gases range in psi valuesfrom about 10 psi to about 100 psi. According to a preferred embodimentof the present invention, each left wing foldable segment 12 a comprisesat least one inflatable rib 26, and preferably at least two: one in themiddle of left wing foldable segment 12 and another at the edge thatforms the hinge point with an adjacent left wing foldable segment 12. Ofcourse, as those of ordinary skill in the art can appreciate, the numberof ribs 26 depends on a variety of factors, and thus the embodiments ofthe present invention are not to be construed as limited to left wingfoldable segment 12 with one, two, or only three ribs 26. As FIGS. 3 and4 illustrate, each left wing foldable segment 12 comprises foldingleading edge 20, spar 16, stringers 30, ribs 26, inflatable joints 36,and composite trailing edge with inflatable joints 38. According to apreferred embodiment of the present invention, spar 16 can be fabricatedfrom a composite material, though this need not be the case. Othermaterials can be used to make spar 16 rigid, including titanium,aluminum, plastic, and other materials. According to still a furtherexemplary embodiment of the present invention, spar 16 can also be madeinflatable (i.e., a prism inflatable structure or substantially uniformpolyhedron structure).

II. Inflatable Ribs with Inflatable or Rigid Stringers and Trailing Edge

According to a preferred embodiment of the present invention, there is arib 26 at each hinge point in left wing foldable segment 12. Asdiscussed briefly above, one or more ribs 26 can be located within eachleft wing foldable segment 12 between hinge points. According to a firstpreferred embodiment of the present invention, a first configuration ofrib 26 comprises a plurality of linked, circular cross section tubes 40.According to a preferred embodiment of the present invention, use oflinked, circular cross-section tubes 40 allows rib 26 to be made in anyairfoil shape required. FIG. 4 illustrates a side view of rib 26according to an embodiment of the present invention. Rib 26 is made upof a plurality of tubes, 40 a-40 d, that are substantially circular(though they need not be, as one of ordinary skill in the art of thepresent invention can appreciate), and are interconnected, at one ormore locations, by tube link 44. In the embodiment shown in FIGS. 4, 5A,and 5B, there is only one tube link 44, so that the drawing is notcluttered; according to an exemplary embodiment of the presentinvention, there can be several tube links 44 so that the gas that isinput to tubes 40 of rib 26 can more easily flow to the other tubes 40.Between each tube 40, there is tube connecting area 42 (e.g., 42 a, 42b, 42 c, 42 d), which is a flat piece of material to connect tubes 40together, and to help provide a definite shape to rib 26. A rib 26 thatis formed in this manner may be created from a mold wherein, forexample, molten plastic under high pressure is forced into a diecreating the inflatable structure. Alternatively, the rib may be createdby appropriately sewing plastic impregnated cloth sheets. Such means formanufacturing inflatable devices are well known, and shall not bediscussed further, for purposes of brevity and clarity. As shown in FIG.5B (which corresponds to a view of rib 26 at line 5B-5B, of FIG. 4),there are no tube links 44, because at that location, and otherssimilarly situated, only tube connecting area 44 exists between tubes40.

According to another exemplary embodiment of the present invention, rib26 can be manufactured from one circular cross section tube, as shown inFIG. 6, where the tube is specifically woven to have the proper airfoilshape in the side view, both for thickness and camber. For example, rib26 can be made of a material, such as Vectran fiber, that can be braidedaround a rigid mandrel of the proper shape, and consist of fiberorientations to maintain that shape when inflated.

According to another exemplary embodiment of the present invention, rib16 can be manufactured from one circular cross section tube, as shown inFIG. 6, where the tube is specifically woven to have the proper airfoilshape in the side view, both for thickness and camber. For example, rib16 can be made of a material, such as Vectran fiber, that can be braidedaround a rigid mandrel of the proper shape, and consist of fiberorientations to maintain that shape when inflated.

The number and location of stringers 30 is selected to give good controlof the airfoil shape of the deployed wing. The wing aft of spar 16 iscovered with flexible membrane skin 46, similar to the cloth thatcovered aircraft wings. According to a preferred embodiment of thepresent invention, the pressure in the inflated ribs provides the forceto tension the flexible membrane skin 46, as shown in FIG. 6.

According to a preferred embodiment of the present invention, ribs 26are inflated with high pressure gas 32, as shown in FIG. 3, as arestringers 30. Low pressure gas 34 is input to spars 16, which is thenused to inflate folding leading edge 20, as discussed in greater detailbelow. Both high pressure gas 32 and low pressure gas 34 can come from apressure tank (not shown), from a chemical reaction gas generator (alsonot shown), or from the exhaust of the propulsion engine.

FIGS. 7 and 8 illustrate operation of foldable leading edge 20 accordingto an embodiment of the present invention. While the previouslydescribed folding system allows a large wing to be folded into a smallvolume, in some cases, even greater compaction is needed. In this case,the wing leading edge could be made to fold also. The aerodynamicallycritical foldable leading edge 20 comprises two components: foldingleading edge shell 50 and leading edge flexible membrane 28. Foldingleading edge shell 50 can be made of an appropriately molded compositeshell part. Alternatively, leading edge shell 50 can be made from knownmetals or alloys. Leading edge shell 50 continues around the leadingedge onto the front lower surface of foldable wing structure 8. However,leading edge shell 50 of foldable leading edge 20 stops well in front ofthe lower front face of spar 16, and the gap is bridged by leading edgeflexible membrane 28. Leading edge shell 50 is attached to the upperfront corner of spar 16 with hinge 52 that allows leading edge shell 50to fold downwards. Leading edge flexible membrane 28 is large enoughthat leading edge shell 50 can fold entirely under spar 16, greatlydecreasing the volume of foldable wing structure 8.

III. Drooping Semi-Rigid Leading Edge

Referring to FIGS. 3 and 7, low pressure gas 34 is received into spar 16from fuselage 10. A plurality of spar air holes 48 exhaust low pressuregas 34 into folding leading edge 20. As shown in FIG. 7, leading edgeshell 50 hangs downward, relative to wing foldable segment 12, fromhinge 52. Hinge 52, as those of ordinary skill in the art of the presentinvention can appreciate, can be a true hinge (i.e., interlockingcylindrical members with a center pin), or can be a simple piece offlexible material acting as a hinge. As low pressure gas fills spar 16,it begins to exit spar 16 via spar air holes 48 into an interior sectionor chamber 51 of leading edge shell 50. Chamber 51 is created by theinterior portion of leading edge shell 50, and membrane 28. Low pressuregas 34 fills chamber 51, and causes membrane 28 to pull taut, as shownin FIG. 8. Once chamber 51 is completely filled, leading edge segment 20is fully formed and joined with the balance of foldable wing segment 8to form an effective airfoil. As an alternative method, higher pressuregas may be used to inflate some number of bladders or air bags withinthe leading edge to provide the deployment force.

Referring to FIG. 3, low pressure gas 34 is received into spar 16 fromfuselage 10. A plurality of spar air holes 48 exhaust low pressure gas34 into folding leading edge 20. As shown in FIG. 7, leading edge shell50 hangs downward, relative to wing foldable segment 12, from hinge 52.Hinge 52, as those of ordinary skill in the art of the present inventioncan appreciate, can be a true hinge (i.e., interlocking cylindricalmembers with a center pin), or can be a simple piece of flexiblematerial acting as a hinge. As low pressure gas fills spar 16, it beginsto exit spar 16 via spar air holes 48 into an interior section orchamber 51 of leading edge shell 50. Chamber 51 is created by theinterior portion of leading edge shell 50, and membrane 28. Low pressuregas 34 fills chamber 51, and causes membrane 28 to pull taut, as shownin FIG. 8. Once chamber 51 is completely filled, leading edge segment 20is fully formed and joined with the balance of wing foldable wingsegment 8 to form an effective airfoil. As an alternative method, higherpressure gas may be used to inflate some number of bladders or air bagswithin the leading edge to provide the deployment force.

According to an exemplary embodiment of the present invention, foldablewing structure 8 can be folded in a spiral configuration, as shown anddescribed in reference to FIGS. 9-13, and 15. According to a preferredembodiment of the present invention, several features are preferablypresent in order to spirally fold foldable wing structure 8: foldablewing structure 8 preferably has at least three wing foldable segments12, preferably four: e.g., 12 a, 12 b, 12 c, 12 d; each foldable wingsegment 12 preferably contains a spar 16 to carry the major loads;substantially the entire airfoil aft of spars 16 comprises a combinationof collapsible, inflatable, and flexible elements, such thatsubstantially the entire airfoil aft of spar 16 can be substantiallycollapsed and stowed in the aft part of spar 16 of each foldable wingsegment 12; and at the junction of spars 16, there is hinge 54 (e.g., 54a, 54 b, 54 c, 54 d) with an axis of rotation that is approximately, butnot exactly, perpendicular to the plane of foldable wing structure 8.

IV. Spiral Fold Spar

FIGS. 14A-C illustrate a hypothetical wing structure in which a hinge isprovided that is substantially perpendicular to the plane of the wing.The purpose of FIGS. 14A-C is to illustrate why spiral wing hinge 54needs to be at an angle other than substantially perpendicular to theplane of foldable wing structure 8. As shown in FIG. 14A, thehypothetical wing comprises two segments, A and B; each are joinedtogether by hinge g, which is substantially perpendicular to plane P ofthe hypothetical wing. FIG. 14B illustrates what happens when segments Aand B are folded together: they are nearly perfectly aligned—point d ofsegment B is adjacent to point c of segment A. FIG. 14C illustrates thesubstantially perpendicularity of hinge g. In contrast, according to apreferred embodiment of the present invention, spiral foldable wingstructure 12 comprises spiral wing hinge 54 that is offset fromperpendicular as shown in FIG. 15. In FIGS. 15A-15G, simplified diagramsof foldable wing segments 12 a and 12 b are shown to illustrate theembodiments of the present invention. In FIG. 15A, foldable wing segment12 a is rotationally hingedly connected via hinge 54 to foldable wingsegment 12 b. The angle of offset θ is shown to be about 4.7° (i.e., anangle of offset from perpendicular). The angle of offset θ can bebetween 1 and 5° according to a preferred embodiment of the presentinvention. In FIG. 15B, foldable wing segment 12 b has been rotatedabout hinge 54; because the angle of offset θ was set to 94.7° in thedirection shown, foldable wing segment 12 b folded under foldable wingsegment 12 a. FIG. 15C is a perspective view of foldable wing segments12 a and 12 b, and FIGS. 15D-15G illustrate the spatial relationshipbetween foldable wing segments 12 a and 12 b as foldable wing segment 12b is rotated through about 180° with respect to foldable wing segment 12a.

FIGS. 14A-C illustrate a hypothetical wing structure in which a hinge isprovided that is substantially perpendicular to the plane of the wing.The purpose of FIGS. 14A-C is to illustrate why spiral wing hinge 54needs to be at an angle other than substantially perpendicular to theplane of foldable wing structure 8. As shown in FIG. 14A, thehypothetical wing comprises two segments, A and B; each are joinedtogether by hinge g, which is substantially perpendicular to plane P ofthe hypothetical wing. FIG. 14B illustrates what happens when segments Aand B are folded together: they are nearly perfectly aligned—point d ofsegment B is adjacent to point C of segment A. FIG. 14C illustrates thesubstantially perpendicularity of hinge g. In contrast, according to apreferred embodiment of the present invention, spiral foldable wingstructure 12 comprises spiral wing hinge 54 that is offset fromperpendicular as shown in FIG. 15. In FIGS. 15A-15G, a simplifieddiagram of foldable wing segments 12 a and 12 b are shown to illustratethe embodiments of the present invention. In FIG. 15A, foldable wingsegment 12 a is rotationally hingedly connected via hinge 54 to foldablewing segment 12 b. The angle of offset θ is shown to be about 4.7°(i.e., an angle of offset from perpendicular). The angle of offset θ canbe between 1 and 5° according to a preferred embodiment of the presentinvention. In FIG. 15B, foldable wing segment 12 b has been rotatedabout hinge 54; because the angle of offset θ was set to 94.7° in thedirection shown, foldable wing segment 12 b folded under foldable wingsegment 12 a. FIG. 15C is a perspective view of foldable wing segments12 a and 12 b, and FIGS. 15D-15G illustrate the spatial relationshipbetween foldable wing segments 12 a and 12 b as foldable wing segment 12b is rotated through about 180° with respect to foldable wing segment 12a.

If spiral wing hinge 54 includes an angle of offset θ, then the endportion of foldable wing segment 12 a, when folded back at about 180°,will lie partially on top of, or below, the end portion of foldable wingsegment 12 a (as shown and described in FIGS. 9-13). According to apreferred embodiment of the present invention, angle of offset θ isbetween about 1° and about 4°.

Because spiral wing hinge 54 is attached to spar 16 with an angle ofoffset θ, the hinge line is canted slightly in a front (or rear) view,such that spars 16 of respective inboard and outboard foldable wingsegments 12 a-d are not parallel to each other, but instead, accordingto a preferred embodiment of the present invention, the end of theoutboard foldable wing segment 12 d is displaced upwards or downwardscompared to the end of the inboard foldable wing segment 12 a byapproximately the thickness of spar 16. The angle of offset θ is chosenso that the end of the next segment 12 can lie entirely above theprevious one; that is, spiral wing hinge 54 a is offset so that the tipof wing foldable segment 12 d lies above the root of wing foldablesegment 12 c when folded, thus allowing wing foldable segment 12 c to beentirely above wing foldable segment 12 b, and so on.

According to an exemplary embodiment of the present invention, use ofangle of offset θ with spiral wing hinge 54 allows the additionalfoldable wing segments 12 b-d to be folded such that a third foldablewings segment 12 c from the wing root will lie entirely above firstfoldable wing segment 12 a from the wing root. If there is a fourthfoldable wing segment 12 d, it will lie above second foldable wingsegment 12 b.

According to a preferred embodiment of the present invention, adeployment method is provided that substantially minimizes the peakdeployment load for deploying foldable wing structure 8. According tothe method of deployment, the first step comprises unfolding spiral winghinge 54 d (shown in FIG. 13) located between the side of fuselage 10and first foldable wing segment 12 a. Spiral wing hinge 54 d joinsfoldable wing structure 8 to short wing segment 12 x (which is notfoldable, but considered a wing segment for purposes of our discussion),at first foldable wing segment 12 a. Arrow A indicates how foldable wingstructure 8 is attached to wing structure 12 x and fuselage 10. Oncefirst foldable wing segment 12 a is deployed, as shown in FIG. 13 (notethat when first foldable wing segment 12 a is deployed away fromfuselage 10, foldable wing segments 12 b-d are still folded andundeployed, resting upon first foldable wing segment 12 a), then spiralwing hinge 54 c is deployed, wherein spiral wing hinge 54 c (shown inFIG. 13), located between first foldable wing segment 12 a and secondfoldable wing segment 12 b is rotated, thereby deploying second foldablewing segment 12 b, resulting in foldable wing structure 8 as shown inFIG. 12.

Following deployment of second foldable wing segment 12 b about spiralwing hinge 54 c, third foldable wing segment 12 c can be deployed byrotating it about spiral wing hinge 54 b, as shown in FIG. 12. Accordingto an exemplary embodiment of the present invention, each foldable wingsegment 12 rotates clockwise when viewed from above and facing fore ofthe aircraft. After third foldable wing segment 12 c rotates aboutspiral wing hinge 54 b, a foldable wing structure 8 appears as shown inFIG. 11. The final rotation of foldable wing segment 12 d then occursabout spiral wing hinge 54 a (shown in FIG. 11), resulting in thefoldable wing structure 8 as shown in FIG. 10. Note in FIGS. 10-13, thelocation of wingtip 56; if a plot were to be made of the position ofwingtip 56 in regard to a plane of foldable wing structure 8, the plotof the position of wingtip 56 would rotate and spiral inward and upwardin regard to the root of foldable wing structure 8.

Following complete spiral deployment of foldable wing segments 12 a-d,the aft trailing edge portion 24 of foldable wing structure 8 isdeployed, as shown in FIG. 9. According to an exemplary embodiment ofthe present invention, deployment of left and right foldable wingstructures 8 a, 8 b can occur simultaneously, or one after the other.According to a preferred embodiment of the present invention, theaforementioned and detailed discussion of method of spiral deployment offoldable wing structure 8 provides a method of foldable wing deploymentwherein the longest moment arm during a deployment is the length of onefoldable wing segment 12.

V. Pneumatic Deployment of Foldable Wing Structure Via Inflatable Ribs

Referring to FIG. 16, inflatable spar extending rib 58 is shown withspars 16 a, 16 b in a deflated state. Hinge 52 connects spar 16 a and 16b together, and membrane 46 provides a sealed path for low pressure gas34 to travel. Spar gas hole 48 passes low pressure gas 34 from spars 16a, 16 b into inflatable spar extending rib 58. In the deflated state,inflatable spar extending rib 58 folds neatly between spars 16 a, 16 b.Adjacent to spar 16 a is right arm 60 a of inflatable spar extending rib58 and adjacent to spar 16 b is left arm 60 b of inflatable sparextending rib 58. As low pressure gas begins to fill inflatable sparextending rib 58, both arms 60 a, 60 b fill with low pressure gas 34 aswell, extending in both directions, respectively, thereby pushing onspars 16 a, 16 b in the direction of each other. The low gas pressuregives a positive deployment moment for the full 180 degrees of hinge 52travel. According to another alternate embodiment of the presentinvention, arms 60 a, 60 b can even be woven as part of spars 16. Thegas to inflate the spar tubes and ribs can come from a pressure tank,from a chemical reaction gas generator, or from the exhaust of thepropulsion engine.

Following complete inflation of inflatable spar extending rib 58, theconfiguration of spars 16 a, 16 b and inflatable spar extending rib 58as shown in FIG. 17. As can be seen, right arm 60 a still pushes againstand is adjacent to spar 16 a, while left arm 60 b pushes against and isadjacent to spar 16 b. The main body of inflatable spar extending rib 58extends backwards, aft of spars 16 a, 16 b to ensure deployment ofstringers 30 and trailing edge 38 components, as discussed in detailabove.

Following complete inflation of inflatable spar extending rib 58, theconfiguration of spars 16 a, b and inflatable spar extending rib 58 asshown in FIG. 17. As can be seen, right arm 60 a still pushes againstand is adjacent to spar 16 a, while left arm 60 b pushes against and isadjacent to spar 16 b. The main body of inflatable spar extending rib 58extends backwards, aft of spars 16 a, b to ensure deployment ofstringers 30 and trailing edge 38 components, as discussed in detailabove.

According to an alternate embodiment of the present invention, hinges 52in spar 16 can be deployed by any of several exemplary options, such asa motor and gear train at each hinge, or a tensioned wire or cable inthe wing leading edge.

The present invention has been described with reference to certainexemplary embodiments thereof. However, it will be readily apparent tothose skilled in the art that it is possible to embody the invention inspecific forms other than those of the exemplary embodiments describedabove. This may be done without departing from the spirit and scope ofthe invention. The exemplary embodiments are merely illustrative andshould not be considered restrictive in any way. The scope of theinvention is defined by the appended claims and their equivalents,rather than by the preceding description.

All United States patents and applications, foreign patents, andpublications discussed above are hereby incorporated herein by referencein their entireties.

What is claimed is:
 1. A foldable wing for use in a very high altitudeaircraft capable of operating at an altitude at or above 85,000 feet,the foldable wing comprising: a first spar section, a second sparsection, and a third spar section, wherein the first spar section ispositioned closest to a fuselage of the very high altitude aircraft, thesecond spar section is positioned adjacent to the first spar section,and the third spar section is positioned adjacent to the second sparsection and farthest away from the fuselage; a first hinge and a secondhinge, wherein the first hinge rotationally connects the first sparsection to the second spar section at a first angle, and wherein thesecond hinge rotationally connects the second spar section to the thirdspar section at the first angle, and further wherein the third sparsection is configured to rotate substantially 180° such that anoutermost portion of the third spar section is located vertically abovean innermost portion of the second spar section, and further wherein thesecond spar section is configured to rotate substantially 180° such thatan outermost portion of the second spar section is located verticallyabove an innermost portion of the first spar section, and the outermostportion of the third spar section is located vertically above anoutermost portion of the first spar section, and wherein each of theplurality of spar sections is configured to receive and transfer a gas,the received and transferred gas causing each of the plurality of sparsections to rotate.
 2. The foldable wing according to claim 1, furthercomprising at least a fourth spar section and a third hinge, the fourthspar section being configured to rotate substantially 180° such that anoutermost portion of the fourth spar section is located vertically abovean innermost portion of the third spar section.
 3. The foldable wingaccording to claim 1, wherein the first angle has a measure of betweenabout 1° and about 4°.
 4. A method for operating a foldable wing for usein a very high altitude aircraft capable of operating at an altitude ator above 85,000 feet, the method comprising: positioning a first sparsection, a second spar section, and a third spar section, such that (i)the first spar section is positioned closest to a fuselage of the veryhigh altitude aircraft, (ii) the second spar section is positionedadjacent to the first spar section, and (iii) the third spar section ispositioned adjacent to the second spar section and farthest away fromthe fuselage; positioning a first hinge to rotationally connect thefirst spar section to the second spar section at a first angle;positioning a second hinge to rotationally connect the second sparsection to the third spar section at the first angle; rotating the thirdspar section with respect to the second spar section substantially 180°such that an outermost portion of the third spar section is locatedvertically above an innermost portion of the second spar section;rotating the second spar section with respect to the first spar sectionsubstantially 180° such that an outermost portion of the second sparsection is located vertically above an innermost portion of the firstspar section, and the outermost portion of the third spar section islocated vertically above an outermost portion of the first spar section;and provide a gas to each of the plurality of spar sections to causeeach of the plurality of spar sections to rotate with respect to anadjacent spar.
 5. The method according to claim 4, further comprisingthe step of rotating a fourth spar section with respect to the thirdspar section at a third hinge, substantially 180° such that an outermostportion of the fourth spar section is located vertically above aninnermost portion of the third spar section.
 6. The method according toclaim 4, wherein the first angle has a measure of between about 1° andabout 4°.